Magnetic latch



H. C. WILSON MAGNETIC LATCH Sept. 29, 1959 2 Sheets-Sheet 1 Filed Jan. 24, 1955 lll 24a Zva 27a sept. 29, 1959 K H. c. wlLsoN MAGNETIC LATCH 2 Sheets-Sheet 2' Filed Jan. 24, 1955 E @fm I7 n 4 C w w W United States Patent O 2,906,553 MAGNETIC LATCH can Wilson, Sherman oaks, Calif. Application January 24, 1955, Serial No. 483,458 s claims. (c1. 292-2515) This invention relates to a permanent magnet construction and to a method of making the same, and is particularly directed to a small and powerful magnetic latch for the doors of kitchen cabinets and the like. The present application constitutes a continuation-impart of my co-pending application Serial No. 403,226, liled J anuary ll, 1954, for Magnetic Latch and Method of Making the Same, now abandoned.

With the advent of permanent magnet alloys having an extremely high degree of retentivity and strength, it has become increasingly popular to form door latches as cooperating magnet and armature elements, the magnet element being conventionally mounted on a stationary mem.- ber, such as a cupboard shelf, and the armature or core element being mounted on the door itself. Such arrangements have the advantage that they provide an extremely Strong and effective latching action and do not tend to become damaged and lose their effectiveness with the passage of time. Furthermore, magnetic latches have high sales appeal since they constitute a novel variation from the ordinary resilient-type latches. However, it has heretofore been an extreme disadvantage of magnetic latches that the permanent magnet alloy employed therein is so expensive that the overall price of the unit is much greater than that of a resilient latch. In fact, several magnetic latches now on the market retail fora price of more than a dollar apiece, whereas resilient latches may be purchased for less than twenty-five cents. A further disadvantage of previously known magnetic latches is that they are either formed with armatures which are always rigid, so that they will not at any time align themselves to a position flush with the magnet face, or are so expensive as to furtherincrease the cost of the device.

In View of the iabove factors characteristic of the field of magnetic door latches, it is an object of the invention to provide a small and inexpensive, yet extremely strong, permanent magnet structure particularly adapted for use as the magnet element of a magnetic latch, and also to provide a self-aligning magnet armature of a simple and effective type.

A further Object of the invention is to provide a permanent magnet having a first component formed of permanent magnet alloy, a second component formed of magnetizable material of a relatively cheap variety not having permanent magnet characteristics, and a third component formed of non-magnetizable material, said components being so constructed, arranged and treated that the resulting permanent magnet has a strength many times the strength of the rst component alone.

A further object of the invention is to provide a method of manufacturing a strong permanent magnet unit incorporating only a small percentage of expensive magnetic alloy.

A further object of the invention is to provide a permanent magnet assembly embodying a laminated pole piece formed of magnetizable material and operable to increase the strength and life of the device.

Other objects and advantages of the invention will be more Ifully set forth in the following specification and claims considered in connection with the attached drawings to which they relate.

In the drawings:

Figure l is a perspective View illustrating the magnetic latch as adapted to hold a cabinet door in closed position against a cabinet shelf;

Figure 2 is a vertical central sectional view through the magnetic latch illustrated in Figure 1;

Figure 3 is a horizontal section taken along line 3 3 of Figure 2;

Figure 4 is la plan yview illustrating a stamped sheet metal element prior to its bending into the casing shape illustrated in Figures 1-3 Figure 5 is a perspective view of a second embodiment of the invention, in which the casing is of different construction;

Figure 6 is a plan yView of the stamped blank for the casing shown in Figure 5;

Figure 7 is a perspective view corresponding generally to Figure 5 but illustrating a third embodiment of the invention, in which a laminated pole piece is employed;

Figure 8 is an enlarged Vertical section taken along line 8 8 of Figure 7, but showing the latch in mounted condition and Figure 9 is a perspective view of one of the components of the laminated pole piece.

Referring first to the embodiment shown in Figures 1-4 of the drawings, the permanent magnet unit of the invention comprises a block 10 of a strong permanent magnet alloy, a casing 11 formed of a relatively inexpensive magnetizable material such as soft steel, and spacing means 12 to maintain block 10 out of engagement with casing 11 except at the casing base wall 13. In a preferred construction, the casing is rectangular in shape and is open ended at its portion opposite base wall 13, there being a rim 14 in the plane of the forward or outer face 15 of magnet block 10 and forming therewith the operating face of the unit. The relative sizes of block 10 and casing 11 are such that a substantial peripheral channel is formed therebetween and completely surrounding the side walls of the block, this gap being filled with the spacing means 12 which may comprise any non` magnetizable substance. Preferably, the spacing means 12 consists of lead poured into the unit while in a molten state.

With the above arrangement, the magnet pole at the inner block face or end 18, and which is in surface contact with the central portion of casing base wall 13, is, in effect, brought around to the casing rim 14 and to the region of outer block yface or pole 15. It follows that both north and south poles are present at the working face ofthe unit to provide an extremely strong attractive force. The magnet unit thus constructed, and when pr'epared in accordance with the method of the invention to be set forth subsequently, has a strength at least six times as great as the strength of the permanent magnet alloy block 10 alone.

Referring particularly to Figure 4, there is shown a piece of stamped sheet metal, preferably soft steel, prior to its folding or bending along the dashed lines into the shape of the casing 11. In addition to the base wall 13 previously mentioned, the stamped sheet metal is adapted to be bent into a top wall 21, a bottom wall 22, and two side walls 23. Formed integral with the outer edge of each side wall 23 is a wing member 24 having a longitudinal slot 26 formed therein to permit adjustment of the casing on its support member. Preferably, the upper surface of each wing member 24 is serrated, as indicated at 27, to provide for the gripping of the wing members K against an underlying surface.

It is a feature of the invention that the armature which face. Preferably, the seat Washer 31 is `dished away froml the underlying Isurface and is formed with a central aperture 32 having a diameter slightly greater than the inner diameter of the bead or ridge 30 on washer 29. InV the mounting of the armature element, a screw 33 is inserted through the apertures in washers 29 and 31 and into'the supporting surface, theV screw head being countersun'k into washer 29 so as to prevent its engaging the magnet face. To facilitate self-alignment of the armature during mounting ofthe device, the outer surface of bead 30 is made spherical about a` point on the axis of screw 33;:

It will be apparent that the magnetic latch may'` be employed on any cupboard or cabinet door, or on lockers,

walk-in closets, or any other place where a latching action.

against free movement but insufficient to prevent it frombeing shifted as force is'exerted against door 381 Thus, the forceful closing of the door operates to shift the casing to the proper adjusted position, after which the screws 37 are further tightened to permanently maintainl the casing in its proper location.

In mounting the armature unit the screw 33 is first tightened completely and is-then backed off an eighth to aquarter of a turn, in order to permit washer 29 to pivot to self-aligned position when door 38 is closed forcefully. After the washer 29 is thus self-aligned, screw 33 is again tightened to holdl thel Washer permanently in aligned position; It is then known that washer 29 will be in'full edge contact instead of full-face contact. In addition,.the

permanent mounting ofwasher 29 -in self-aligned position is extremely important since it prevents rattling'thereof. It is evident, however, that with the present devicel a' new alignment may be achieved easily should warping, of the door or shelf occur.

Referring next to Figuresrand 6, a second embodiment is illustrated which is the same as theiirst embodiment except Afor the shape of the casing,the corresponding parts being given like reference numerals followed by the letter La As shown in Figure 6, the stamped blank for the casing is such that the base Wall 13a is thecenter part of a cross member, and the top, bottom, and side4 walls 21a, 22a, and 23a, re'spectivcly,'fo`rm the arms: of the cross. As distinguished from the embodiment shown in Figure 4, the wings 24a are not'respectively'integral with the `side walls, but instead are connectedby a com-y ponent 41 which is integral with-one'edge of top wall 21a.

As illustrated in Figure 5, the component 41 and wingl members 24a are reverse bent relative to the top Wall 21a, and the top, bottom, and side walls are bent at right angles to base wall 13a tocompletefthe structure".V

Referring next to Figures 7-9, a third embodimentr isf illustrated in'whichlikeparts' have been'given'like reference numeralsfollowed by the letter IL Thecasing'llb is substantially the same as that shown inFigures landr 2, .exceptthat 4apertures "'45 'areprovidedl for introduction In mounting the magnet unit, the screws of the lead 12b or similar spacing material. In contrast to the previous embodiments, the block 10b of permanent magnet alloy does not extend into contact with the washer or armature 29, but instead terminates in a surface 46 which is set back a substantial distance from the rim of the casing. A plurality of corresponding square laminations 47 formed of magnetizable material such as soft steel, are mounted in the casing 11b in contact With surface 46. Two or more laminations 47 are employed in surface engagement with each other, and the outer lamination has its outer surface lying in the' sam'e plane as ther rim offthe-casingi The-laminations 47y are provided about their peripheries with longitudinal channels 48 (Figure 9) iri order to maintain them in aligned position and to facilitate pouring of the lead 12b.

It has been discovered that the provision of the laminated pole piece between the permanent magnet alloy 10b and armature 29 operates" to increase'thel life' of the permanentV magnet assembly, andV that when the pole piece is formed of two or more laminations 47, inI surface engagement* with eachV other and with-the1perm`anent magnet` alloy and armature, the over-all strength ofthe assembly is greatly-Y increased. y It isi-thus possiblelwith they embodiment off- Figures 7-9V to form a permanent magnet assembly having a strengthas great` as that' of the embodiments shownin Figures l-6, but using atsubstantially smaller amountv of permanent magnet alloy' 10b; Thisl is, of course, of extreme importance since` the cost of the permanent alloy isa veryvsubstantial' factorVV in-the`overallcost of the assembly.

in the polepiece laminations. 47,-these aperturesbeing of a size to receive the-head- 52 of-screw 33;A Preferably, thescrew head 52-,is'justV slightly lesser in diameter than the-apertures'Sl-so that the screw may be bar'elyv inserted into the apertures during mounting of the unit. With the described arrangement, the magnet unit is first mounted on shelf 36 and the screw 33,which-is `formed of magnetizable material, is inserted into the apertures 51 where# upon it is held magnetically in'contact'with surface-46 ofthemagnet alloy 10b. The'door 38 isthen closed tocontact the point of screw 33, which makes a slight -Vmark on the door. It is thus known the exact'point at whichthe screw 33, andfwashe'rs29 and 31, should bemounted,

and screw 33 is inserted at the point marked on thegdoor` by the above process. operation idescribedin connection with the` previous errr-` bodirnents is then carried out. There has thusbee'n'de` scribedan extremely simple and accurate means by which a novice-'may mount an-armature in perfect-registered position relativeltol the magnet.-

Stated generally, and for all formsof'theinvention;

to produce the permanent magnet effect. Preferably, the magnet alloy is in an unmagnetized condition `when it' is placedinfthe casing andthe spacingmeans'providiso` that a magnet only results after the assembled compo# nents :are treated! in the-magnetic-eld.- Whenv thus assembledand'treated, themagnetic action at'thelwo'rking'? face of the-unitis, as previously indicated,VY atlt'ez'rstl siX times as great as the magnetic'actio'n ofthe magnetic alloy 10,10ag-or 10b alone.

It is of-interest tofnote that-upon disassembly'iofthev magnetic alloyv element fromthe casing,- there is' substantially no magnetism in the casing, and-*the magV netism ofI the alloy is-relatively weak-5 Furthermore,Y upon reassembly of the alloy element 10 with the'cas-l ing, the'iresulting magnet unit is relatively weak and must again be treated ina magneticfield before a strongY permanent magnet will rmult.

It is important `that thepermanent'magnet 10, 10a orl 10b beformed of a` permanentv magnetV alloy having The tightening `or `self-aligning anisotropic properties, that is to say having a preferred axis of magnetization. More particularly, the permanent magnet alloy is one having anisotropic properties and which has been directionally magnetized during its manufacture. Directional magnetization may be accomplished by providing an anisotropic alloy, heating the same to just below its melting temperature, placing the heated alloy in a strong unidirectional lield, cooling the alloy while in the field, and then demagnetizing the cooled yalloy with an alternating current field. Although demagnetized, the manufactured alloy material still has its directional properties.

The block 10, a or 10b of such directional magnetic alloy is then inserted within the casing so that its preferred axis of magnetization extends longitudinally thereof, or perpendicular to wall 13, 13a or 13b. After the magnet unit has been assembled as described above, it is placed in a magnetic ield in which lines of magnetic force line up with the preferred axis of magnetization of the alloy block, or again perpendicular to wall 13, 13a or 13b.

A preferred directional magnetic alloy is known as Alnico 5, and is formed of 8 percent aluminum, 14 percent nickel, 24 percent cobalt, 3 percent copper and 51 percent iron. Another directional magnetic alloy is known as Alnico 6 and is formed of 8 percent aluminum, 15 percent nickel, 24 percent cobalt, 3 percent copper, 1.25 percent titanium, and the balance iron. A magnetic alloy trade-mark Cunife also has directional properties and is formed of 60 percent copper, percent nickel and 20 percent iron. Another directional magnetic alloy is Vectolite and comprises 30 percent Fe2O3, 44 percent Fe304, and 26 percent C0203. All of these materials may be purchased from the General Electric Company, and all except Cunife are manufactured by the heat treating process set forth above. Cunife is diierent in that it develops a preferred axis of magnetization along the direction of working i.e. rolling, drawing, or swaging.

While the particular method and device herein shown and described in detail are fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that they are merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.

I claim:

1. In a magnetic latch device of the type having a casing formed of magnetizable material vand adapted to be secured to a stationary cabinet element, said casing having a base wall and an open end remote from saidA base wall, a block of permanent magnet material disposed in said casing and in surface contact with said base wall, means to maintain said block in spaced relation from the side wall of said casing, that improvement which comprises an armature assembly including a first washer adaptedto seat against a door, a second washer of magnetic material having an annular bead portion adapted to seat on the inner rim of said lirst washer, and a clamping screw adapted to be inserted through said first and second washers and into said door to hold said washers against said door in a predetermined adjusted position wherein the outer face of said second washer lies flush against the face of said latch device casing when said door is closed.

2. The invention as claimed in claim 1 characterized in that the surface of said casing adapted to contact said cabinet element is serrated in a manner preventing relative movement therebetween.

3. In a magnetic latch device of the type having a casing magnetizable material open on one end face and adapted to be secured to a cabinet well adjacent the open side thereof, a permanent magnet having one end resting against the end of said casing opposite said open end face with its side walls spaced from the casing side walls, said magnet side walls being appreciably shorter than the side walls of said casing, non-magnetic material tilling the space between said magnet and casing side walls, ring means of magnetizable material interposed between the open end of said casing and the adjacent face'of said magnet, that improvement which includes armature means adapted to be mounted on a movable closure member and engageable against the open end of said latch casing for holding said' closure member closed, said armature means including a pair of self-aligning washers with dierent size inner openings, the washer with the smaller opening being outwardly beaded with said bead seating against the inner rim edge of the Washer with the larger one or" said openings, the outer one of said washers being of magnetic material, vscrew means for clamping said washers together and to a closure member with the outer one of said washers positioned to lie flush against the open end face of said latch casing when said closure member is in closed position.

4. In a magnetic latch device comprising a one-piece casing of non-magnetic material having mounting tabs projecting therefrom for supporting said device on a cabinet adjacent an open side thereof, a permanent magnet located against the bottom wall of said casing and spaced from the other walls and the open end of said casing, non-magnetic material holding said magnet spaced from said casing walls, that improvement which comprises ring means of magnetizable material spaced from said casing walls by said non-magnetic material and having one face lying ush with the open end of said casing and its opposite face lying against the end of said magnet, said ring means forming an opening to receive the head of a mounting screw for an armature adapted to be mounted on the cabinet door whereby the closure of the door against the end of a screw supported in said opening accurately establishes the proper mounting place on the door for the latch armature, said armature comprising a pair of self-aligning washers adapted to be mounted on the cabinet door by said screw with the face or" the outer washer adjusted to lie hush against the open end of said latch casing when the cabinet door is closed and means for clamping said armature immovably to a cabinet door with said outer washer clamped in said adjusted position.

5. A magnetic latch device as dened in claim 4 characterized in that said one-piece latch casing is formed from a sheet metal blank having tabs folded at right angles to one another to form a casing open on one face only thereof and having integral latch-mounting tabs projecting laterally from at least one wall thereof.

References Cited in the le of this patent UNITED STATES PATENTS 190,343 Lash May 1, 1877 622,620 Greenawalt Apr. 4, 1899 2,219,186 Hornfeck Oct. 22, 1940 2,392,592 Iseld Ian. 8, 1946 2,432,819 Schumacker Dec. 16, 1947 2,493,624 Gerson I an. 3, 1950 2,514,927 Bernhard July 11, 1950 2,519,435 Byrd Aug. 22, 1950 2,609,221 Schultz Sept. 2, 1952 2,657,342 Stem Oct. 27, 1953 2,694,592 Borchers et al Nov. 16, 1954 2,695,808 Manchester Nov. 30, 1954 2,697,804 Phelon Dec. 21, 1954 2,701,158 Schmitt Feb. 1, 1955 FOREIGN PATENTS 814,855 Germany Oct. 29, 1951 

